PIR Sensor

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PIR Sensor

Post by tuneking » Fri Apr 01, 2016 10:23 am

I am using a PIR (HC-SR501) that has a 5 volt input. I want to use it to turn on a laser requiring 4.5 volt input. But when the PIR is energized, the output is only 2.8 volts, not enough to power my laser. Is something wrong with the laser? Is there a way to alter the PIR? Or could I add another battery in series to increase the voltage available to the laser? Any thoughts would be appreciated.

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Re: PIR Sensor

Post by TS-Chris » Tue Apr 05, 2016 9:11 am


Your PIR module probably doesn't have the ability to deliver the amount of current a laser needs let alone the voltage.

What you want to do is have the PIR module turn on a transistor or MOSFET, and then have the transistor/MOSFET drive the laser from a suitable power source. Something like the SparkFun MOSFET Power Control Kit is probably overkill for a small laser, but would be an easy way to make this work.

If you have any other questions shoot us an email at techsupport@sparkfun.com.

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